Motor braking device



A118- 16, 1949- lr;. R. GoLDFlELD 2,479,344

MOTOR BRAKING lDEVICE Filed Got. 26, 1944 I INVENTOR. Enwm Russen GoLoFiLLD rltenwu nl-lg. su urea MOTOR BRAKIN G DEVICE Edwin Russell Goldiieid, University Heights, Ohio, assignmto Picker X-Ray Corporation Waite Manufacturing Division, Inc., Cleveland, Ohio, a corporation of.0hio

Application October 26, 1944, Serial No. 560,481

This invention relates to improved braking means for electric/motors.

An object of the present invention is to provide a brake for the rotor of an electric motor which is continuously urged toward braking position and` which is released by means of a magnetic armature which is attracted to an electromagnetic pole piece of the motor whenever the same is magnetized.

A particular application of my invention occurs in connection with a shaded pole induction motor where the magnetic armature for releasing the brake is positioned adjacent the shading coil.

A further modication of my invention occurs in the provision of a shading ring on the magnetic armature which is attracted to the electromagnetic pole piece ior the purpose ci releasing the brake.

@ther objects and advantages of the present invention and the details adopted in practicingmy invention will be apparent from the accompanying drawings and description, and the essential features will be set forth in the accompanying claims.

in the drawings,

lig. l is a perspective viev.7 of a small motor equipped with my improved device,

Fig. 2 is a ragmental sectional view taken along the line t-- or Fig. l;

Fig. 3 is a view similar to Fig. 2 but showing the brake in released position;

Fig. e is a side elevational view oi the device ci i; while idg. 5 is a ragiuentai perspective view showing one end or the magnetic armature of lllg. l.

The purpose ci the present invention is too quickly stop the rotor oi an electric motor when the energizing electric current is turned oil. Unless such means is provided, the inertia of the rotor and the driven parts connected therewith is such that it will not come to rest quickly enough when the current is turned oil and it is essential in most applications that the speed ci stopping be accurately controlled. Braking devices are Well known in which a brake shoe bears against some part connected with the rotor at all times when the motor is not energized. Then this brake is released usually by means of a solenoid which is energized simultaneously with the motor. My present improvement accomplishes the same purpose but without the use of -a separate solenoid.

The drawings show my invention as applied to -a shaded pole induction motor of small size and adapted to revolve at about 3,300 R. P. M. The motor illustrated comprises a rotor I9 mounted 4 Claims. (Cl. 172--36) in suitable bearings for rotation between pole pieces l I and l2 which in the present embodiment are shown of laminated construction. These poles are magnetized in the usual manner by means of the fixed winding i3 which is energized by means not shown in the usual manner when current is A supplied to the motor. The motor shown is provided with shading coils i4 which rest in suitable recesses or grooves I5 in the pole pieces. On the upper end of the rotor shaft is ixed a brake drum i6 which rotates with the rotor. The entire motor is mounted on a base il.

The braking means is mounted on a bracket i8 in fixed relation to the base il and having an upstanding :flange portion ita, at the upper end of which two ears ido are provided extending outwardly at right angles to the flange portion. Located centrally of the upper edge of the flange portion is a tongue lilo for supporting a spring as later described.

A lever it is provided with notches lila intermediate itsends into which the ears ib extend to provide a iulcrum. igor the lever. The upper end ci the lever is provided with a braise shoe i9?) adjacent the brake drum iii. The lower end of the lever is provided with a magnetic `armature idc secured to the lever oy the screws 2t. The ends oi this armature are bent inwardly as at iSd to points adjacent the pole pieces li and i2. A tongue ide extends upwardly and outwardly from the bottom of the lever to a point opposite the tongue idc. it small coil spring 2i is held in tension between the tongues itc and itc. Luis spring is positioned .above the ulcrum of the lever and therefore serves to continuously pull the shoe lh against the drum it.

it results from the above construction that when current is supplied to the winding i3 upon starting the motor, the pole pieces il and l2 are niagnetized which in turn. will attract the armature E9e and release the brake vshoe lilo from the drum i6. This action takes place because of the high stray or leakage ilus which exists around the pole pieces of the motor. This is particularly true in the locality of the shading coils i4 where the flux is greater. l, therefore, prefer to position the ends |903 of the magnetic armature adjacent these shading coils as shown.

For substantially reducing or eliminating chatter between the armature IBc and the pole pieces, I may provide a shading ring 22 on the armature and at right angles to the plane of the shading coils I4. As best seen in Figs. 1 and 5, the ends I9d of the armature |9c are bifurcated, and the shading ring 22 of copper or other suitable metal is xed to one of these bifurcated ends Ill. The shading rings 22 are positioned generally parallel to a plane passing through the rotor and pole pieces. In this manner,- an out-of-phase ilux is provided which substantially reduces chatter of the armature during energization'of the motor.

In the above manner I have provided a very eillcient means for braking the rotor immediately upon the deenergization of the motor including the coil I3 and have also provided very simple means for releasing the brake immediately upon the energization of the coil I3 which ls a standard part of the motor shown and does not require any extra electrical devices.

What I claim is: f

1. Braking means for an electric motor having a rotor and electromagnetic pole pieces supporting the iield windings of said motor and said motor having a shading coil on at least one of said pole pieces, comprising a brake drum rotatable with said rotor, a brake shoe adjacent said drum, means urging said brake against said drum, and means for moving said shoe away irom said drum including a magnetic armature positioned to receive the magnetic nux diverted by said shading coil.

2. Braking means for an electric motor hav- .ing a rotor and electromagnetic pole pieces sup,l

porting the iield windings of said motor and said motor having a shading coil on et least one of said pole pieces, comprising a brake drum rotatable with said rotor and positioned laterally upon said pole pieces, a lever having a fulcrum intermediate its ends, a brake shoe at one end of said lever positioned adjacent said brake drum, a magnetic armature at the other end of said lever and positioned to receive the magnetic ux of said shading coil, and spring means urging said shoe against said drum, said armature being adapted when attracted by said pole piece to move said shoe away from said drum.

3. Braking means for an' electric motor having a rotor and electromagnetic pole pieces and having a shading coil on at least one of said pole pieces. comprising a brake drum rotatable with .said rotor and positioned laterally upon said pole pieces, a lever having' a fulcrum intermediate its ends, a brake shoe at one end of said lever positioned adjacent said brake drum, a magnetic armature at the other end of said lever, a shading ring on said armature and adjacent said shading coil, said shading ring lying in a plane generally at right angles to the plane of said shading coil, and spring means urging said shoe against said drum, said armature being adapted when attracted by said pole piece and shading coil to move said shoe away from said drum, and said shading ring being adapted to reduce chatter.

4. Braking means for an electric motor having a rotor and electromagnetic pole pieces comprlsing a brake drum rotatable with said rotor, a brake shoe adjacent said drum, means urging said brake against said drum, means for moving said shoe away from said drum including a magnetic armature positioned adjacent at least one of said pole pieces, and a shading ring on said armature opposite said one pole piece and extending generally in a plane parallel to a plane passing through said rotor and pole pieces, whereby to substantially reduce chatter of said armature.

WIN RUSSEL GOLDFIELD.

REFERENCES CETIED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 363,186 Thomson May 17, 1887 728,974 Pott et al May 26, 1903 1,005,857 Lindquist Oct. 17, 1911 1,437,421 Holliday Dec. 5, 1922 1,518,020 Traver Dec. 2, 1924 1,689,442 Lexa Oct. 30, 1928 1,768,950 Frank July 1, 1930 1,822,679 Stewart et al. Sept. 8, 1931 

